The conventional stator assembly of a cooling fan, disclosed in the Taiwan Patent No. 221590, includes a chassis with a base thereof, containing a room; a circuit board disposed in the room of the chassis with several positioning holes set on some appropriate places of it; a coil base wound with coil, also disposed in the room of the chassis adjacent to the circuit board; a position device set on the coil base; which is characterized in that:
Several identical position holes are disposed on the base of the chassis corresponding to the position holes of the circuit board. Several position bars are disposed on one side of the position device adjacent to the circuit board for sequentially placing the position bars in the position holes of the base and the position holes of the circuit board.
The small stator assembly of a cooling fan, disclosed in the Taiwan Patent No. 236471, includes a stator assembly coil, upper and lower magnetic poles, a circuit board, and a case, which is characterized in that:
A metal tube with a specific outside diameter passes through the stator assembly coil, upper and lower magnetic poles, and the center of the circuit board. The button of the metal tube is pressed in the hole of the center of the case.
The small stator assembly of a cooling fan, disclosed in the Taiwan Patent No. 223374, includes a stator assembly coil, upper and lower magnetic poles, a circuit board, and a case, which is characterized in that:
Circular lip with a larger outside diameter is disposed on the top of the metal tube with a single outside diameter. The diameter of the circular lip is larger than the inside diameter of the central hole of the upper and lower magnetic poles and the stator assembly coil. The outside diameter of the metal tube is slightly larger than the inside diameter of the central hole of the upper and lower magnetic poles and the circuit board, and is a little bit smaller than the inside diameter of the central hole of the stator assembly coil. The button of the metal tube presses through the upper magnetic pole, the stator assembly coil, and the lower magnetic pole. The stator assembly coil chipped tightly in the outside diameter of the lower part of the circular lip of the metal tube. Then, by the central hole of the circuit board, the circuit board is pressed to form a combined stator assembly outside the case, which will be moved into the case later. Since the outside diameter of the metal tube is slightly larger than the inside diameter of the central hole of the case, the metal tube is forced into the inside diameter of the central bar of the case, so that the whole stator assembly will be firmly mounted in the case.
Although all of the above methods can mount the stator assembly on the outside frame body of the fan, in the stator assembly of a cooling fan disclosed in Taiwan Patent No. 221590, the position bar must cooperate with the position hole. Since the position bar is very small, it might be broken by extra force during fabrication or storage process.
In the small stator assembly of a cooling fan, disclosed in Taiwan Patent No. 236471 and No. 223374, the stator assembly coil presses the metal tube so as to position the stator assembly. Thus, after a certain time, the metal tube and the stator assembly will get loose or fall off to interrupt the rotation operation of the fan due to the metal characteristic of elements. Therefore, it is apparent that the above conventional structure is insufficient for real practice.